Internal Vanadium Doping and External Modification Design of P2-Type Layered Mn-Based Oxides as Competitive Cathodes toward Sodium-Ion Batteries.

Abstract

P2-type layered manganese-based oxides have attracted considerable interest as economical, cathode materials with high energy density for sodium-ion batteries (SIBs). Despite their potential, these materials still face challenges related to sluggish kinetics and structural instability. In this study, a composite cathode material, Na0.67 Ni0.23 Mn0.67 V0.1 O2 @Na3 V2 O2 (PO4 )2 F was developed by surface-coating P2-type Na0.67 Ni0.23 Mn0.67 V0.1 O2 with a thin layer of Na3 V2 O2 (PO4 )2 F to enhance both the electrochemical sodium storage and material air stability. The optimized Na0.67 Ni0.23 Mn0.67 V0.1 O2 @5wt %Na3 V2 O2 (PO4 )2 F exhibited a high discharge capacity of 176 mA h g-1 within the 1.5-4.1 V range at a low current density of 17 mA g-1 . At an increased current density of 850 mA g-1 within the same voltage window, it still delivered a substantial initial discharge capacity of 112 mAh g-1 . These findings validate the significant enhancement of ion diffusion capabilities and rate performance in the P2-type Na0.67 Ni0.33 Mn0.67 O2 material conferred by the composite cathode.